Electrically driven compressor



4 Sheie'cs--Shem l 21.1. i ....M 000000000000000000 0000000000000000000v00n0n000n00 000000000 0 0000000000 000000000000000000 0 0 00N0N0000N0 0 0 00 May '17, 193s.

G. SZEKELY ELECTRICALLY DRIVEN COMPRESSOR Filed Feb. 11, 1935 May 17, 1938. @.SZEKELY 2,117,863

ELECTRICAIJLIY DRIVYEN COMPRESSOR Filed Feb. ll, 1935 4 Sheets-Sheet 5 May 11, 1938. G. szEKELY 2,117,863

Y ELECTRICALLY DRIVEN COMPRESSOR Filed Feb. 11, 1935 4 sheets-sheet 4 bay@ v I Patented/May 17, 1938 UNITED STATES PATENT OFFICE application February 11, 1935, serial'Nn. 5,916 In Austria February 26, 1934 IClaim.

nating magnetic iield which sets up and mainj tains the vibrations of the system, and has for its l object to improve the resonance conditions at a certain output, and also to extend the range of output within which a favorable working condition prevails.

What has hitherto stood in the way of the employment of compressors of this description has been the drawback that the most favorable resonance conditions are only realized when working to a certain definite end pressure, and that the deflection or throw of the vibrations falls off very considerably when the end pressure deviates but very slightly lfrom the ideal. 'Ihe present invention is based upon recognition of the fact that this disadvantageous behaviour is largely due to the linear characteristic of the vibrating means and resilient elements hitherto usual in the drive employed in such devices, with the result that on alteration of the pneumatic force or resistance there is brought about an alteration in the resultant spring force acting upon the vibrating mass which is sumcient to destroy the state of resonance.

In order to overcome this unfavorable inuencing of the state of resonance conditioned by the curvature of the compression characteristic, the present invention proposes the employment of spring means for the vibrating system which have a non-linear curve for the power developed expressed as a function of the course, It thus becomes possible, more particularly when the characteristic of the spring means employed is` upwardly curved, to bring about `a condition of vibration which approximates far more closely to the character of harmonic oscillations than does the condition of vibration set up'with the l5 employment of springs of linear characteristic.

Compressors constructed in accordance with the invention thus show a more favorable state of working, when the output is adJUsted to a certain pressure, than the hitherto known compressors,

o since resonance is invariably far more easily realized in a harmonically vibrating system than when the vibration is non-harmonic or pseudoharmonic. A further advantage of the invention which is of particular importance is that the mean `5 rise of the resultant spring characteristic changes,

less, when working to diil'ermt end pressure, with the employment of springs of non-linear than with the employment of springs of linear characteristic, with the result, under practical workn ing conditions, tint the state of resonance is maintained over a wider range of end pressures than has hitherto been the case.

As springs of non-linear characteristic it is advisable to employ conical springs which are so made that, when stressed, the lower turns become 5 gradually applied to the supporting foundation, so that the number of eifective turns diminishes and the power increase is augmented per unit of depression. 'I'he non-linear characteristic of the g spring means employed can, however, also be 10 obtained in other ways, for example by the use of materials the natural resiliency of which possesses the desired non-linear character, such as is the case for example with vulcanized rubber.

A form of construction for a compressor unit 15v in accordance with the invention is shown, by way of example, in the accompanying drawings, in whichr- 2 Fig. 1 is a sectiona1 view of the compressor uniti zo Fig. 2 isl a side view of the same taken partly in section of Fig. 1;

Fig. 3 is a plan view of the same;

Fig. 4 shows a modiiled construction of the spring means;

Fig. 5 is a graphic representation of output curves.

In the constructional example shown in Figures 1 to 4 of the drawings I denotes the electromagnet which drives the compressor, the coil 2 of this magnet being traversed .by current derived from an alternating current main and thereby caused to exert upon the armature 3 an attraction Vwhich fluctuates periodically in intensity. The electromagnet I has a circuit in iron which is as far as possible closed, in order to provide maximum electromagnetic output with minimum weight and space requirement. For this same reason the number and size of the air gaps 4, 4', I" which interrupt the iron circuitl are kept down to a minimum, and the same end is also served by the sloping ofthe air gaps 4 and l" relatively to the direction of vibration of the armature I.v k

To the armature 8 is attached the lower end of the bifurcated connecting rod 5 which is made up of laminated material, and which is provided at its upper end with the arched or cambered base plate 6 oi' the piston. The body 1 of' the piston, which is made of rubber, is attached to 50 this plate 6 by means of the embedded.and vulcanized-in ring 8 and of the'clamps 9. The marginal portion 'la of the body 1 of the piston is of Slight thickness so that it is in the nature of a diaphragm, and is clamped, together with the re- 55 maining parts of the compressor, in a ring Ill supported in the uprights Il of the framework o! the' unit. The hitherto described parts of the vibrating system, namely the armature 3, the pieten l, andthe connecting rod l. should bemade f SII as light as possible, in order to-reduce inertia resistance to a minimum, and this fact is taken. account of inthe shaping and construction oi these parts.

The base plate 6 of the compressor piston is resiliently supported against the stationary part of the unit by means of a block of rubber i3 which is supported on a cross head I2 bridging the uprights II. This rubber block I3 is a resilient massive body of elastic material which can be tuned to the desired frequency by suitable shaping, and the characteristic curve of which is non-linear and likewise capable of being lniluenced in a desired sense by suitable shaping of the block. In lieu of this elastic body i3 it is also possible to employ a tapered helical spring tia as the supporting or bearing spring of the vibrating system, as indicated in Fig. 4. In rie-- signing the springing means employed for the vibrating piston care must also be taken to make this spring, which likewise pertains to the totality of the vibrating system, as light as possible in weight. In order to allow for compensation ofany alteration in the initial tension of the spring means I3 or I3a which may occur in the course of use, and thus to obviate any alteration of the inherent frequency or characteristic of these means, and also to admit of accurate adjustment of the initial tension of the spring means, the cross head I2 is adjustable upon the uprlghts II by means of nuts I4. The rubber block I3 is prevented from shifting its position by the provision of centering studs i5 and I5'.

Between the compressor piston 'I and the cover IG, which is disposed opposite the same and is likewise clamped peripherally in the ring III, there is enclosed the working chamber I1 of the compressor in which the intake, compression, and expulsion of the working medium is eifected. In the cover I6 there are arranged the suction and the pressure valve of the compressor, so that the vibrating piston comprises no valve parts to add to its total mass. The employment of an independently acting suction valve'necessltates. however, that its moving parts be so constructed that they are capable of keeping up with the rapid working rhythm of the compressor according to the invention. It is therefore advisable to make the suction valve disk--and the same applies also to the pressure valve disk-as lightI as possible in weight, and to makeit of such shape that it can open and close with the frequency ofthe piston vibration or with even higher frequency. In the constructional example shown in the drawings this result is achieved bythe use of a rubber suction valve disk I8 which is thickened in the middle so as to be of lentil shape, and the marginal portion of which covers over theV suction apertures I9 provided in the cover I6. The'suction valve c lisk I8 is attached to the cover 'I6 by means of a screw 2h which ensures the requisite initial tension of the disk. The pressure valve 2I takes the form of an annular diaphragm provided with apertures 22 which are disposed in olf-set relation to corresponding apertures 23 in the cover II..v

The cover I6 of the compressor is so shaped that, when the suction valve disk I8 is inserted in position, the clearance, provided the stroke of the piston is suillciently long, is reduced to a Given. such designing of the working chamber, it becomes possible, by suitable tuning of the inherent frequency of the vibrating system to the frequency oi the magnetic force and by correct dimensioning of the 'stroke-limiting counterforces, to provide a. stroke volume oi the compressor member which practically completely lls out the working chamber of the compressor. Over the plate i8 there are provided thesuction chamber 21 with the suction pipe connection 24, and the'compression chamber 25 with the compression pipe connection 26. The hoods 2l and 2! enclosing these chambers, respectively, are attached to the cover I6 and-to the ring Il, respectively, and can readily be detached, together with the cover I6, after slackening of the screws 30. The electromagnet I and the uprights II rest upon feet 3I and 32 which are preferably made of soundand shock-absorbing material.

The non-linear characteristic of the spring means associated with the piston not only improves the character of the vibrations, but also helps to prevent the length of the compressor strobe from being in general influenced by the output ci* the compressor to any appreciable extent, since the resonance once set is maintained in the various working states of the ccmpressor.,

This will be clearly understood by having reference to Fig. 5 in which the ordinates give the output of the compressor (in litres per hour) referred to the state at suction, and the e the end excess pressure (in atm.) of compressed air. The broken line I represents the output characteristic obtained in a` particular case with a compressor having springing means of linear characteristic; after replacement of this spring by a spring of non-linear characteristie there was obtained the more favorable curve represented bythe full line 1I.

In Figs. 1 and 2 of the drawings there is shown the lowest position of the `vibrating system (piston and armature) under normal Working conditions. If under exceptional working conditions the maximum amplitude of vibration should happen to become exceeded, the increasing of such a tendency beyond the admissible limit is prevented by the lower surface 33 of the armature coming in contact with the opposite surface 3| on the core of the electromagnet, or by the body 1 of the piston striking against the cover I6. Related subject matter was described in applicants abandoned application Serial No. 761,140, died December 6, 1935.

I claim:

An electromagnetlcally driven compressor or vacuum pump having, in combination, an electromagnet comprising a stationary magnet body, a coil arrangedthereon for energizationby an alternating electrical current of given frequency and a vibratile armature in position to be attracted by said magnet body upon energization of said coil, a reciprocating compressor member connected to said amature and forming therewith a freely oscillating unit, and resilient restor- 'ing means connected to said unit so as to resist its deviation from a given position and tuned to a natural frequency which causes the oscillation of theunit to be substantially in resonance with the periodic force of attraction of the electromagnet, said resilient means comprising a conical helical spring arranged for having its effective' number of turns reduced and, accordingly the coemclent of resilience increased when the load acting upon the spring is increased.

GEORG SZKELY. 

